sort by Rank | Alpha
| Possible Meanings | Rank |
| Organizational Leadership | **** |
| Okidata Laser | **** |
| Optical Limiter | **** |
| Orchard Lake | **** |
| Oiseau Lyre | *** |
| Orientation Leader | *** |
| Occupational License | *** |
| Orient Lines | *** |
| Oaklyn Library (Oaklyn, NJ) | *** |
| Oakville Library (Oakville, WA) | *** |
| Oakwell Library (San Antonio, TX) | *** |
| Oceana Library (Oceana, WV) | *** |
| Oceanfront Library (Virginia Beach, VA) | *** |
| Oceanport Library (Oceanport, NJ) | *** |
| Ochlocknee Library (Ochlocknee, GA) | *** |
| Ocracoke Library (Ocracoke, NC) | *** |
| Odenton Library (Odenton, MD) | *** |
| Odessa Library (Odessa, MO) | *** |
| Odum Library (Valdosta, GA) | *** |
| Ogeechee Library (Savannah, GA) | *** |
| Oneida Library (Oneida, NY) | *** |
| Oneida Library (Oneida, WI) | *** |
| Ortonville Library (Ortonville, MN) | *** |
| Otis Library (Norwich, CT) | *** |
| Otisville Library (Otisville, MI) | *** |
| Ottawa Library (Ottawa, KS) | *** |
| OUHSC Library (Del City, OK) | *** |
| Owens Lake | *** |
| oral leukoplakia | *** |
| Operating Locations | *** |
| Order Contact Lens | *** |
| Opaque Liquid | ** |
| optic layer | * |
| Ocean Logic | * |
| octahedral layer | * |
| Operational Left | * |